As is well known in the electrographic fixing art, various apparatus adapted to apply heat and pressure have been found useful to permanently fuse images composed of heat-softenable electrographic toner particles to a receiving member, such as a plain paper copy sheet. Such apparatus generally includes at least one fixing member having a surface bearing an adhesive (i.e., non-stick) composition to prevent "offset" of toner particles during the fixing process, i.e., adherence of heat-softened toner particles onto the surface of the fixing member. In one typical embodiment of such fixing apparatus, there is provided at least one pair of rollers which are arranged in a parallel fashion and are adapted to be rotatably driven to advance a heat-softenable toner-bearing paper web therebetween. At least one of the rollers useful in such an apparatus possesses an inner core or cylinder having one or more outer adhesive layers disposed thereon. Means are provided in such an apparatus such that at least one of the rollers which contacts the heat-softenable toner-bearing web is heated to a temperature sufficient to produce tackification of the toner particles. Such heat can be applied to the heated roller by a source of radiant energy, steam and/or a resistance coil located in the roller core, or can be applied by an external directional source of thermal energy.
As noted above, it is known in the electrographic fixing art (in order to prevent offsetting of toner particles onto the surfaces of fixing members, e.g., the roller(s) of the above-described fusing apparatus) that it is desirable to provide one or more of the rollers with a coating of a material known for its "adhesive" qualities, i.e., its release characteristics. It is also desirable that such adhesive materials should exhibit excellent chemical and physical stability when subjected to long periods of exposure to relatively high heat conditions, e.g., temperatures greater than about 120.degree. C., and high pressure conditions, i.e., lineal pressures greater than about 2.5 kg./cm.
Extended research and development activity has been undertaken to discover classes of materials useful as adhesive covering materials in fixing devices such as the above-described "roller-fuser" apparatus. However, to date, the art has relied almost exclusively on a handful of specific polymeric materials including various silicone elastomers, and certain fluorocarbon-containing polymers such as Teflon (a trademark of E. I. duPont de Nemours and Co. for hompolymers of tetrafluoroethylene and various copolymers of tetrafluoroethylene and other fluorinated olefins such as hexafluoropropylene) and certain fluorocarbon-based elastomers such as various vinlidene fluoride-based elastomers which contain hexafluoropropylene as a co-monomer, e.g., Viton.RTM. A (vinylidene fluoride-hexafluoropropylene) and Viton.RTM. B (vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene), both of which are also available from the duPont Company. Among the various publications in the art which disclose fusing devices employing one or more abhesive materials of the types noted immediately hereinabove are U.S. Pat. No. 3,268,351, issued Aug. 23, 1966; U.S. Pat. No. 3,666,247, issued May 30, 1972; an article entitled "Electrographic Fusing Apparatus" appearing in the July 1972 issue of Product Licensing Index at pages 72-73; and in U.S. Pat. No. 3,795,033, issued Mar. 5, 1974.
Various support members having abhesive covering compositions selected from certain of the materials described above have been found useful as fixing members in commercial electrographic fusing devices. However, it has generally been found necessary to also incorporate in or on the surface of such abhesive compositions various so-called "wicking oils" or "release liquids". Such wicking oils generally include various fluorocarbon liquids, silicone liquids, or fluorosilicone liquids and are necessary to increase the release characteristics of the fixing member(s) used in the fusing device. In addition, it has also been found that it is necessary to add various filler materials to many of the abhesive coating materials noted above to increase the thermal stability and/or mechanical strength of the resultant abhesive composition so that it can withstand the high temperatures and pressures which are used in fusing devices.
As a consequence of the foregoing problems associated with many of the known abhesive compositions used in fixing devices such as those described in the aforementioned publications, there is a need to find improved abhesive-surfaced fixing members for use in such devices.